Bloch Spectrum Definition

A concept relating to energy spectra . Let H be the one-dimensional Schrödinger equation operator H = - \frac{d^2}{dx^2} + U_\alpha, where Uα is a periodic function of period α. The Bloch spectrum of H is the set of values E for which all the solutions of (H − E)φ = 0 are bounded on the whole real axis .